1. Field of the Invention
The present invention relates to a thermosetting resin composition comprising a thermosetting resin as a main component and a silane compound.
2. Description of the Related Art
In recent years, vigorous researches are being made on plastic materials exhibiting a high resistance to heat, a low hygroscopicity, and a low internal stress in an attempt to provide construction materials used in the manufacture of general industrial equipments, automobiles and space engineering equipments. The plastic materials of this type include, for example, engineering plastic materials such as an epoxy resin, polyimide resin, PPS (polyphenylenesulfide), and PES (polyethersulfone). These plastic materials are used in the form of a resin composition prepared by adding a curing agent and other suitable additives to these plastic materials depending on the use of the plastic materials.
However, the conventional resin composition fails to meet simultaneously all of the requirements for a high resistance to heat, a low hygroscopicity and a low internal stress, making it difficult to use the conventional composition as construction materials in various fields.
In the field of semiconductor devices, resin compositions containing as a main component a thermosetting resin such as an epoxy resin are widely used as an encapsulating resin for a semiconductor element. The resin composition of this type exhibits, when cured, excellent properties including a high resistance to humidity, a high moldability, and satisfactory electrical properties under high temperatures and, thus, is widely used for molding.
However, the miniaturization of each functional unit on a semiconductor element and the enlargement of the semiconductor element pellet itself are being promoted rapidly in accordance with the prominent progress achieved in recent years in the integration of the semiconductor element. These changes in the semiconductor element pellet have now caused the conventional encapsulating resin to fail to satisfy the severe requirements such as a high resistance to a thermal shock. To be more specific, if a large pellet having a fine surface structure is encapsulated with a resin composition containing as a main component the conventional thermosetting resin, splitting tends to take place in the phosphosilicate glass film or the silicon nitride film serving to protect an aluminum wiring pattern formed on the surface of the pellet. Also, the encapsulating resin itself tends to be cracked. The cracking is serious particularly where a sample is subjected to a thermal cycle test (TCT test). Naturally, the appearance and reliability of the semiconductor device are markedly impaired.
What should also be noted is that, when a semiconductor device is soldered to a substrate in mounting the semiconductor device, the entire apparatus receives a severe thermal shock. Specifically, the entire apparatus is exposed to an atmosphere of such a high temperature as 200.degree. to 260.degree. C. for 5 to 90 seconds. In this step, the moisture taken into the package is evaporated so as to bring about cracking in the encapsulating resin.
For dealing with these splitting and cracking problems, vigorous studies are being made in an attempt to develop an encapsulating resin of a low internal stress, which exhibits an excellent resistance to cracking when a cured material obtained by using the encapsulating resin receives a thermal shock. It is known to the art that the internal stress of a cured material formed from an encapsulating resin can be lowered by adding a silicone oil or a silicone rubber to the resin composition. Where a silicone oil is simply added in the step of preparing a resin composition, however, the silicone oil bleeds off when the resin composition is molded or cured. As a result, the appearance of the molded article is impaired. Also, the mold is stained in many cases. On the other hand, in the case of adding a silicone rubber, the melt viscosity of the resin composition is increased, giving rise to problems such as reduction in the mechanical strength of the encapsulating resin.
As a measure for overcoming the above-noted problems inherent in the prior art, a technique of adding a silicone oil or a silicone rubber having a functional group such as a hydroxyl group to a resin composition is disclosed in, for example, Published Unexamined Japanese Patent Application No. 58-34824 and. Published Examined Japanese Patent Application No. 2-34181. However, a resin encapsulated semiconductor device prepared by encapsulating a semiconductor device with the resultant encapsulating resin fails to exhibit a sufficient resistance to a thermal shock. Further, the encapsulating resin leaves much room for further improvement in its resistance to humidity.